Possible Duplicate:
Why the vast difference of opinion about the age of the Universe?
I was surprised my self when I learned that light comes from stars that are millions or billions of light years apart. It seems to be obvious that our universe is pretty old. I suppose.
One explanation is that the word yom in hebrew means era instead of days. Still the Jewish calendar counts from creation. That suggest that you know (or presume to know) the year the world is born.